Methods of making pharmaceutical compositions with enhanced stability

ABSTRACT

The present invention provides for a stabilized biodegradable polymeric composition useful as a controlled release delivery system for peptide agents. The compositions of the present invention comprise a) a beneficial salt of a luteinizing hormone releasing hormone (LHRH) analog formed with a strong acid that minimizes or prevents the interaction/reaction between the LHRH and the polymer in an organic solution; b) a biodegradable polymer; c) a pharmaceutically acceptable organic solvent; and d) optionally one or more excipients. The present invention also relates to a method of manufacturing and a method of use thereof.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/406,321, filed on Jan. 13, 2017, which is a continuation ofU.S. patent application Ser. No. 15/230,413, filed on Aug. 6, 2016,which in turn is a continuation of U.S. patent application Ser. No.11/653,636, filed on Jan. 16, 2007, which claims priority to ProvisionalPatent Application 60/759,891, filed on Jan. 18, 2006. The entirecontents of these applications are incorporated by reference.

BACKGROUND OF THE INVENTION

In recent years, a large number and variety of peptide agents such aspeptides, oligopeptides, polypeptides, and proteins have been discoveredand have received much attention as drug candidates. However, manypeptide agents are not stable as they are easily hydrolyzed or degradedin vivo by enzymes resulting in a very short circulation half-life.Therefore, most of peptide medicines have been administered byinjection, typically multiple times per day.

Injection administration, however, is painful, very costly, andinconvenient. Often, the patient compliance is very challenging. Formany peptide agents, particularly hormones, it requires the drug to bedelivered continuously at a controlled rate over a long period of time,and thus a controlled release delivery system is desirable. Such systemsmay be provided by incorporating the peptide agents in biodegradable andbiocompatible polymer matrices. In one approach the polymer is dissolvedin an organic solvent and then mixed with the peptide agents that isfabricated into the forms of microcapsules, microgranules or implantablerods by removing the organic solvent. The peptide agent is entrappedwithin the polymer matrices. Several products have been successfullydeveloped by using biodegradable polymers in the forms of microparticlesand solid rod implants, such as Lupron, Zoladex, Triptorelin, etc.Although these products appear to be effective, but they have drawbacksand limitations, such as the large volume of suspending fluids formicroparticles or surgical insertion of solid implants. These productsare not very patient friendly. In addition, the manufacturing processesfor producing sterile and reproducible products are complicated,resulting in high cost of manufacturing. It is highly desirable that acomposition can be manufactured and used easily.

In another approach, the biodegradable polymer and the peptide agentsare dissolved in a biocompatible organic solvent to provide a liquidcomposition. When the liquid composition is injected into the body, thesolvent dissipates into the surrounding aqueous environment, and thepolymer forms a solid or gel depot from which the bioactive agent isreleased over a long period of time. The following references U.S. Pat.Nos. 6,565,874; 6,528,080; RE37, 950; 6,461,631; 6,395,293; 6,355,657;6,261,583; 6,143,314; 5,990,194; 5,945,115; 5,792,469; 5,780,044;5,759,563; 5,744,153; 5,739,176; 5,736,152; 5,733,950; 5,702,716;5,681,873; 5,599,552; 5,487,897; 5,340,849; 5,324,519; 5,278,202;5,278,201; and 4,938,763 are believed to be representative in this areaand are incorporated herein by reference. Notwithstanding some success,those methods have not been entirely satisfactory for a large number ofpeptide agents that may be effectively delivered by such an approach.

It is well recognized in the art that bioactive agent containing basicfunctional groups interacts with biodegradable polymer to catalyze (orexpedite) the degradation of the polymer and form conjugate with thepolymer and/or its degradation products. The interaction/reactionbetween the basic bioactive agents and polymer carriers may occur: 1)during formulation when the basic bioactive agents are incorporated inthe polymer carrier, such as microencapsulation, injection molding,extrusion molding, mixing with polymer solutions in organic solvent, andthe like; 2) during storage and 3) during the process of biodegradationand the release of bioactive agents in vivo.

It is known that the degradation of peptide agents and biodegradablepolymers, and reactions between the two typically occur much faster insolution than in a dry, solid state. The interaction/reaction betweenbioactive agents containing basic functional groups, i.e., amines, andpolymers during the microparticle formation process using solventevaporation/extraction methods where the bioactive agent and polymerwere dissolved/dispersed in non-polar organic solvents were disclosed[Krishnan M. and Flanagan D R., J Control Release. 2000 Nov. 3; 69(2):273-81]. Significant amount of amide moieties were formed. It wasclearly shown that commonly used solvents for fabrication ofbiodegradable polymer drug delivery systems could permit rapid reactionbetween bioactive agent and polymer. In another disclosure, theaccelerated degradation of polymers by organic amines in polar proticorganic solvent (e.g., methanol) was also reported [Lin W J, Flanagan DR, Linhardt R J. Pharm Res. 1994 July; 11(7):1030-4].

Since the controlled release delivery system is commonly fabricatedthrough a step that involves dissolving/dispersing peptide agent intobiodegradable polymer solution in an organic solvent, the stabilizationof all the components in the composition at this step represents a verysignificant formulation challenge. One common approach that has beenused to overcome the challenge of manufacturing and storage stability ofpeptide agent and biodegradable polymer in solution or suspension is tokeep the peptide agent and the polymer solution in two separatecontainers and mix them just before use. This assumes that the organicsolvent may be separated from polymeric matrix quickly throughdiffusion, extraction or evaporation after the peptide agents andpolymer solution are mixed. An example was disclosed in U.S. Pat. Nos.6,565,874 and 6,773,714 that describe polymeric delivery formulations ofleuprolide acetate that is related to a commercial product Eligard® fortreatment of prostate cancer. In order to maintain the stability of theformulations, this product is supplied in separate syringes and thecontents in the syringes are mixed just before use. However, because ofthe viscous nature of the polymer formulations, it is often difficult tomix the contents in two separated syringes by end users. The uniformityof the formulations prepared by the end-user may vary significantlywhere contamination may also occur and the quality of the treatment canbe compromised significantly. In addition, this approach will notprevent the interaction between the peptide agent and polymer duringmixing and administration. As disclosed in US20060034923 A1, whenoctreotide acetate was combined with polylactide-co-glicolide solutionin NMP, more than 40% of octreotide was acylated within 5 hours. Thismodification of the peptide may lead to a significant loss of activityor change of immunogenicity. The molecular weight of the polymer alsodecreased significantly within the same time period. This fastdegradation of the peptide and polymer will alter the release profile ofthe peptide and result in a compromised treatment outcome. Therefore,precise control for the preparation process and time is critical andthis significantly increases the difficulty for end-user. Furthermore,the in vivo formation of the implant from the injectable polymericcomposition is not instantaneous. Typically the solvent dissipationprocess can take a few hours to several days depending upon the solventsused. During this period, the presence of an organic solvent could alsopromote the interaction/reaction between the peptide agents and thepolymer. Therefore, there is a need to develop a pharmaceuticalcomposition that will minimize or prevent the interaction/reactionbetween the peptide agent and the polymer in an organic solution. Thereis a further need to develop a pharmaceutical composition that is stablewith a satisfactory storage shelf life in a ready-to-use productconfiguration.

SUMMARY OF THE INVENTION

It was surprisingly discovered that injectable biodegradable polymericcompositions comprising peptide agents in the form of a salt formed witha strong acid (e.g., hydrochloric acid) exhibit much higher stabilitythan those in the form of a salt formed with a weak acid (e.g., aceticacid) or in the form of the free base. Such beneficial salts of peptideagents may be formed through the neutralization of any basic groups ofthe peptide agents with a strong acid. When such beneficial salts ofpeptide agents formed with a strong acid were formulated into injectablebiodegradable polymeric compositions, the interactions/reactions betweenthe peptide agents and the polymer are minimized or prevented. Usingsuch beneficial salts of peptide agents formed with a strong acid allowsfor the preparation of a stabilized injectable composition pre-filled ina single syringe in a ready-to-use configuration with satisfactorystorage stability. The use of the salt of peptide agent formed with astrong acid of the present invention to enhance the stability of theinjectable polymeric compositions is not contemplated by the prior art.

Accordingly, the present invention provides a stabilized injectablebiodegradable polymeric composition for forming an economical,practical, and efficient controlled release delivery system for peptideagents. The present invention also provides a method of manufacturingand a method of use thereof. According to the present invention, thedrug delivery system is produced easily and delivered conveniently to asubject such as a mammal or human. The compositions deliver therapeuticamount of peptide agents over a desired, extended period of time,preferably from several weeks to one year. The compositions are bothbiocompatible and biodegradable, and disappear harmlessly afterdelivering the dose of the peptide agents.

The compositions in accordance with the present invention comprise a) abeneficial salt of a peptide agent formed with a strong acid thatminimizes or prevents the interaction/reaction between the peptide agentand the polymer in an organic solution; b) a biodegradable polymer; c) apharmaceutically acceptable organic solvent. According to the invention,the pharmaceutical composition may optionally include excipients toachieve optimal delivery of the peptide agent. The pharmaceuticalcomposition may be a viscous or non-viscous liquid, gel or semisolidthat moves as a fluid so that it may be injected using a syringe. Thepharmaceutical composition may be pre-filled into one syringe to form aproduct in a ready-to-use configuration.

The peptide agent of the present invention contains at least one basicgroup. The peptide agent may be any peptide, oligopeptide, polypeptide,or protein that is capable of providing a biological, physiological ortherapeutic effect in an animal or human. The peptide agent may be anyone or more of known biologically active peptide, oligopeptide,polypeptide, or protein recognized in any documents cited herein orotherwise recognized in the art. The peptide agent may also stimulate orinhibit a desired biological or physiological activity within the animalor human, including without limitation, stimulate an immunogenic orimmunological response.

According to one embodiment of the present invention, the peptide agenthas an N-terminus that is not a primary amine (e.g., LHRH agonists, suchas leuprorelin, goserelin, LHRH antagonists, such as cetrorelix,enfuvirtide, thymosin al, abarelix, and the like). In another embodimentof the present invention, the peptide agent has either an N-terminalprimary amine or side chain primary amine group covalently modified withhydrophilic and/or lipophilic moieties that may be produced throughpegylation, acylation, and the like. Furthermore, both N-terminalprimary amine and side chain primary amine groups of the peptide agentmay also be covalently modified simultaneously with hydrophilic and/orlipophilic moieties through pegylation, acylation, and the like.

The strong acid may be any acid having a pKa in water less than 3,preferably less than 0, more preferably less than −3. For example, astrong acid may be selected from, but not limited to, the groupconsisting of hydrochloric acid, hydrobromic acid, sulfuric acid,organic sulfuric acids, alkyl sulfuric acids of 1-40 carbons, nitricacid, chromic acid, methanesulfonic acid, trifluromethane sulfonic acid,organic sulfonic acids, trichloroacetic acid, dichloroacetic acid,bromoacetic acid, chloroacetic acid, cyanoacetic acid, 2-chloropropanoicacid, 2-oxobutanoic acid, 2-chlorobutanoic acid, 4-cyanobutanoic acid,perchloric acid, phosphoric acid, hydrogen iodide, and the like.

The biodegradable polymer can be any biocompatible and pharmaceuticallyacceptable polymers. The biodegradable polymers may be thermoplastic,which melts upon heating and solidifies upon cooling. The biodegradablepolymers of the invention are substantially insoluble in aqueous or bodyfluid, but are capable of substantially dissolving or dispersing in awater-miscible organic solvent to form a solution or suspension. Uponcontact with an aqueous fluid, the water-miscible organic solventdiffuses/dissipates from the inventive composition, which causes thecoagulation of the polymer to form a gel, or solid matrix encapsulatingthe peptide agent. Examples of the polymers suitable for the presentcomposition includes, without limitation, polylactides, polyglycolides,polycaprolactones, polyanhydrides, polyurethanes, polyesteramides,polyorthoesters, polydioxanones, polyacetals, polyketals,polycarbonates, polyorthocarbonates, polyphosphazenes,polyhydroxybutyrates, polyhydroxyvalerates, polyalkylene oxalates,polyalkylene succinates, poly(malic acid), poly(maleic anhydride), andcopolymers, terpolymers, or combinations or mixtures therein. Lacticacid-based polymers, and copolymers of lactic acid and glycolic acid(PLGA), including poly(D,L-lactide-co-glycolide) andpoly(L-lactide-co-glycolide) are preferably used in the presentinvention. In some embodiments, the PLGA polymers have a weight averagemolecular weights of between about 2,000 to about 100,000 and monomerratios of lactic acid to glycolic acid of between about 50:50 to about100:0.

The pharmaceutically acceptable organic solvents may be selected from agroup consisting of N-methyl-2-pyrrolidone, methoxypolyethylene glycol,alkoxypolyethylene glycol, polyethylene glycol esters, glycofurol,glycerol formal, methyl acetate, ethyl acetate, methyl ethyl ketone,dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, caprolactam,decylmethylsulfoxide, benzyl benzoate, ethyl benzoate, triacetin,diacetin, tributyrin, triethyl citrate, tributyl citrate, acetyltriethyl citrate, acetyl tributyl citrate, triethylglycerides, triethylphosphate, diethyl phthalate, diethyl tartrate, ethyl lactate, propylenecarbonate, ethylene carbonate, butyrolactone, and1-dodecylazacyclo-heptan-2-one, and combinations thereof.

According to the present invention, one or more excipients may beincorporated in the inventive composition to achieve optimal delivery ofthe peptide agent. Suitable excipients may include release ratemodifying agents, burst effect reducing materials, buffering materials,antioxidants, and the like.

According to the present invention, suitable release rate modifyingagents include, but are not limited to, amphiphilic compounds orcopolymers, such alkanecarboxylic acid, oleic acid, alkyl alcohol, polarlipids, surfactants, copolymers of polyethyleneglycol and polylactide orpoly(lactide-co-glycolide), poloxamers, polyvinylpyrrolidone,polysorbates, and the like; esters of mono-, di-, and tricarboxylicacids, such as 2-ethoxyethyl acetate, triethyl citrate, acetyl tributylcitrate, acetyl triethyl citrate, glycerol triacetate, di(n-butyl)sebecate, and the like; polyhydroxy alcohols, such as polyethyleneglycol, sorbitol, and the like; fatty acids; triesters of glycerol, suchas triglycerides, medium-chain triglycerides such as MIGLYOL 810, 812,818, 829, 840, and the like. Mixtures of rate modifying agents can alsobe used in the polymer systems of the invention.

According to the present invention, suitable buffering agents include,but are not limited to, inorganic and organic salts including calciumcarbonate, calcium hydroxide, calcium myristate; calcium oleate, calciumpalmitate, calcium stearate, calcium phosphate, magnesium carbonate,magnesium hydroxide, magnesium phosphate, magnesium myristate, magnesiumoleate, magnesium palmitate, magnesium stearate, zinc carbonate, zinchydroxide, zinc myristate, zinc oleate, zinc palmitate, zinc stearate,zinc phosphate, and combinations thereof.

According to the present invention, suitable antioxidants include, butare not limited to, d-alpha tocopherol acetate, ascorbyl palmitate,butylated hydroxyanidole, butylated hydroxyanisole,butylatedhydroxyquinone, hydroxycomarin, butylated hydroxytoluene, ethylgallate, propyl gallate, octyl gallate, lauryl gallate,propylhydroxybenzoate, trihydroxybutylrophenone, vitamin E, pegylatedvitamin E or vitamin E-TPGS, and the like.

The present invention further provides methods of making and using suchcompositions. For example, a method of making such compositionscomprising the neutralization of basic amine groups of peptide agents toform a beneficial salt to minimize or prevent the interaction/reactionof the basic amine group with the polymer; and the combination of thebeneficial salt with other components and optionally one or moreexcipients. Preferably, the beneficial salt of the peptide agent isformed first, and then combined with the polymer dissolved in an organicsolvent. Such compositions are physico-chemically stable prior to andduring the fabrication process of a controlled delivery system such asmicroparticle formation or other implantable matrix formation.Preferably, such injectable compositions are physico-chemically stableduring preparation, storage, and subsequent administration to a subjectand form consistent and controlled release implants upon administrationto a tissue site.

The present invention further provides a kit for administration of theinjectable composition to form a consistent and controlled release depotsystem, the kit comprises: a biodegradable polymer dissolved in apharmaceutically acceptable solvent; a beneficial salt of a peptideagent containing at least one basic amine group formed with a strongacid dissolved or dispersed in the polymeric vehicle; and optionally oneor more excipients. The uniform mixture of all the components ispackaged into one container. Preferably, the container is a syringe.Accordingly, the present invention also provides a method comprising astep of filling a syringe with the composition to form a stable productin a ready-to-use configuration.

The present invention further provides a method for in-situ formingimplant capable of functioning as a controlled release delivery systemof the peptide agent in a subject. The peptide agent is preferablyincorporated into the in situ formed implant, and subsequently releasedinto the surrounding tissue fluids and to the pertinent body tissue ororgan as the polymer degrades. The method comprises: administration ofthe injectable compositions of the present invention to an implant siteby any suitable method for applying a liquid, as for example, by meansof a syringe, needle, cannula, catheter, pressure applicator, and thelike.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. Stability of LA in Formulations at 4° C. after 16 Months

FIG. 2. Molecular Weight of PLGA in Formulations at 4° C. after 16Months

FIG. 3: Effect of type and concentration of PLGA on the release ofleuprolide

FIG. 4. Effect of vitamin E on the release of LA from injectablecompositions

FIG. 5. Effect of Miglyol 812 on the release of LA from injectablecompositions

FIG. 6. Release profile of LA from injectable polymeric compositionsfollowing SC administration in rats

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a stabilized injectable biodegradablepolymeric composition for forming an economical, practical, andefficient controlled release delivery system for peptide agents. Thepresent invention also provides a method of manufacturing and a methodof use thereof.

The compositions of the present invention comprise a) a beneficial saltof a peptide agent formed with a strong acid that minimizes or preventsthe interaction/reaction between the peptide agent and the polymer in anorganic solution; b) a biodegradable polymer; c) a pharmaceuticallyacceptable organic solvent. According to the invention, thepharmaceutical composition may optionally include one or more excipientsto achieve optimal delivery of the peptide agent. The injectablepolymeric composition of the present invention may be a viscous ornon-viscous liquid, gel or semisolid that moves as a fluid so that itmay be injected using a syringe. The injectable polymeric compositionmay be pre-filled into one syringe to form a product kit in aready-to-use configuration.

The controlled release delivery system of the present invention may beformed as an implantable polymeric matrix in vitro, or alternatively, itmay be formed in-situ in the forms of a gel or a solid implant. Whenadministered to a subject, the controlled release of the peptide agentcan be sustained for a desired period of time depending upon thecomposition of the implant. With the selections of the biodegradablepolymer and other components, the duration of the sustained release ofthe peptide agent can be controlled over a period of time from severalweeks to one year.

The terms “a”, “an” and “one”, as used herein, are meant to beinterpreted as “one or more” and “at least one.”

The term “stabilized”, as used herein, refers to a significantimprovement in the stability of the components in the injectablepolymeric composition, which is necessary to achieve a stable staterequired to develop a viable product. The term “stabilized injectablepolymeric composition” as used herein means that the components, e.g.,the polymer and the peptide agent, of the composition retains at least80%, preferably at least 90%, of their original molecular weight,structure and/or biological activity during manufacturing and afterstorage for an extended time period, e.g., months to years, preferablymore than 12 months, under appropriate conditions.

The term “controlled release delivery”, as defined herein, is intendedto refer to the delivery of a peptide agent in vivo over a desired,extended period of time following administration, preferably from atleast several weeks to one year.

The term “peptide agent” as used herein is in a generic sense to includepoly(amino acids) that are normally generally referred to as “peptides”,“oligopeptides”, and “polypeptides” or “proteins” which are usedinterchangeably herein. The term also includes peptide agent analogs,derivatives, acylated derivatives, glycosylated derivatives, pegylatedderivatives, fusion proteins and the like. The “basic peptide agent” isa peptide which is basic in nature, arising from the presence of basicamino acids, for example arginine or lysine, or arising from theN-terminus of the peptide agent, or simply a peptide agent whichcontains at least one basic group, optionally in the presence of one ormore acidic amino acid groups. The term also includes syntheticanalogues of peptides, unnatural amino acids having basic functionality,or any other form of introduced basicity.

The term “peptide agent” is meant to include any peptide agents havingdiagnostic and/or therapeutic properties including, but not limited to,antimetabolic, antifungal, anti-inflammatory, antitumoral,antiinfectious, antibiotics, nutrient, agonist, and antagonistproperties.

Specifically, the peptide agents of the invention may be any peptidescapable of forming a beneficial salt with a strong acid, in particular apeptide agent containing an electron donor base group such as a basicnitrogen atom, e.g. an amine, imine or ring nitrogen. The peptide agentspreferably contain one or more exposed protonatable aminefunctionalities. Peptide agents useful in the preparation of thecompositions of the present invention include, but are not limited to,oxytocin, vasopressin, adrenocorticotropic hormone (ACTH), epidermalgrowth factor (EGF), platelet-derived growth factor (PDGF), prolactin,luteinising hormone, luteinizing hormone releasing hormone (LHRH), LHRHagonists, LHRH antagonists, growth hormones (including human, porcine,and bovine), growth hormone releasing factor, insulin, erythropoietin(including all proteins with erythropoietic activity), somatostatin,glucagon, interleukin (which includes IL-2, IL-11, IL-12, etc.),interferon-alpha, interferon-beta, interferon-gamma, gastrin,tetragastrin, pentagastrin, urogastrone, secretin, calcitonin,enkephalins, endorphins, angiotensins, thyrotropin releasing hormone(TRH), tumor necrosis factor (TNF), parathyroid hormone (PTH), nervegrowth factor (NGF), granulocyte-colony stimulating factor (G-CSF),granulocyte macrophage-colony stimulating factor (GM-CSF),macrophage-colony stimulating factor (M-CSF), heparinase, vascularendothelial growth factor (VEG-F), bone morphogenic protein (BMP), hANP,glucagon-like peptide (GLP-1), exenatide, peptide YY (PYY), renin,bradykinin, bacitracins, polymyxins, colistins, tyrocidine, gramicidins,cyclosporins (which includes synthetic analogues and pharmacologicallyactive fragments thereof), enzymes, cytokines, antibodies, vaccines,antibiotics, antibodies, glycoproteins, follicle stimulating hormone,kyotorphin, taftsin, thymopoietin, thymosin, thymostimulin, thymichumoral factor, serum thymic factor, colony stimulating factors,motilin, bombesin, dinorphin, neurotensin, cerulein, urokinase,kallikrein, substance P analogues and antagonists, angiotensin II, bloodcoagulation factor VII and IX, gramicidines, melanocyte stimulatinghormone, thyroid hormone releasing hormone, thyroid stimulating hormone,pancreozymin, cholecystokinin, human placental lactogen, human chorionicgonadotrophin, protein synthesis stimulating peptide, gastric inhibitorypeptide, vasoactive intestinal peptide, platelet derived growth factor,and synthetic analogues and modifications and pharmacologically-activefragments thereof.

The preferred peptide agents used herein include the peptide agentswherein the N-terminus is not a primary amine. For example, theN-terminus of the peptide agents may be a pyroglutamic acid, e.g., LHRH,and LHRH agonists such as leuprorelin, buserelin, gonadorelin,deslorelin, fertirelin, histrelin, lutrelin, goserelin, nafarelin,triptorelin, and the like. Alternatively, the N-terminal amine group maybe capped or acylated, e.g., cetrorelix, enfuvirtide, thymosin α1,abarelix, and the like.

The preferred peptide agents used herein also include the peptide agentswherein the N-terminal primary amine is covalently modified withhydrophilic and/or lipophilic moieties such as through pegylation,acylation, and the like. The peptide agents used herein further includethe peptide agents wherein the side chain primary amine(s) arecovalently modified with hydrophilic and/or lipophilic moieties such asthrough pegylation, acylation, and the like. The preferred peptideagents used herein further include the peptide agents wherein bothN-terminal primary amine and side chain primary amine groups arecovalently modified simultaneously with hydrophilic and/or lipophilicmoieties such as through pegylation, acylation, and the like.

The term “hydrophilic moiety” refers to any water-soluble linear orbranched oligomer or polymer including, but not limited to, polyethyleneglycol and polypropylene glycol and similar linear and branchedpolymers. Preferably, the molecular weight of the polymer ranges fromabout 500 daltons to about 50,000 daltons. Hydrophilic polymers for usein the present invention may have a reactive group incorporated forattachment to the peptide agent of interest through amine, carboxylic,hydroxyl, or thiol groups.

The term “pegylation” used herein refers to the covalent conjugation ofa soluble polyethylene glycol to the peptide agents. Polyethylene glycolcan be prepared according to standard protocols with one end capped aswith a methoxy group and the other end activated for facile conjugationto active groups on peptide agents. For examples, various methods forpreparing polyethylene glycols and their use for pegylations aredescribed in the art: [e.g., Roberts M J, Bentley M D, Harris J M,Chemistry for peptide and protein PEGylation. Adv Drug Deliv Rev. 2002Jun. 17; 54(4): 459-76. Veronese F M. Peptide and protein PEGylation: areview of problems and solutions. Biomaterials. 2001 March; 22(5):405-17 and U.S. Pat. Nos. 6,113,906; 5,446,090; 5,880,255], which areall incorporated herein by reference.

The term “lipophilic moiety” refers to any molecules having a solubilityin water at 20° C. less than 5 mg/ml, preferably less than 0.5 mg/ml,more preferably less than 0.1 mg/mL. Such a lipophilic moiety ispreferably selected from C₂₋₃₉-alkyl, C₂₋₃₉-alkenyl, C₂₋₃₉-alkadienyland steroidal residues. The term “C₂₋₃₉-alkyl, C₂₋₃₉-alkenyl,C₂₋₃₉-alkadienyl” are intended to cover straight chain and branched,preferably straight chain, saturated, monounsaturated and di-unsaturatedhydrocarbon of 2-39 carbon atoms.

Introduction of a lipophilic moiety covalently to a peptide agentthereof leads to a lipophilically modified peptide that may haveimproved therapeutic effect comparing to the native molecule. This canbe typically done by reacting an amine group in a peptide agent with anacid or other reactive groups in a lipophilic molecule. Alternatively,the conjugation between peptide agent and lipophilic molecule isaccomplished through an additional moiety such as a bridge, spacer, orlinkage moiety, which can be degradable or non-degradable. Some examplesare disclosed in the prior art, [e.g., Hashimoto, M., et al.,Pharmaceutical Research, 6:171-176 (1989), and Lindsay, D. G., et al.,Biochemical J. 121:737-745 (1971), U.S. Pat. No. 5,693,609, WO95/07931,U.S. Pat. No. 5,750,497, and WO96/29342. WO98/08871, WO98/08872, andWO99/43708]. These disclosures are expressly incorporated herein byreference for describing lipophilically modified peptides and forenabling preparation of the same.

The term “strong acid”, as defined herein, is meant to include any acidswith a pKa less than 3, preferably less than 0, and more preferably lessthan −3. The strong acids suitable for the present invention may beselected from, but not limited to, the group consisting of hydrochloricacid, hydrobromic acid, nitric acid, chromic acid, sulfuric acid,methanesulfonic acid, trifluromethane sulfonic acid, trichloroaceticacid, dichloroacetic acid, bromoacetic acid, chloroacetic acid,cyanoacetic acid, 2-chloropropanoic acid, 2-oxobutanoic acid,2-chlorobutanoic acid, 4-cyanobutanoic acid, pamoic acid, perchloricacid, phosphoric acid, hydrogen iodide, and the like.

The “strong acid” of the present invention also includes any organicsulfuric acids such as alkyl, aryl or alkylaryl sulfuric acids of 1-40carbons, preferably less than 18 carbons, and more preferably less than6 carbons, and organic sulfonic acids such as alkane, arylalkane, arene,or alkene sulfonic acids of 1-40 carbons, preferably less than 18carbons, and more preferably less than 6 carbons.

The term “a beneficial salt of a peptide agent”, as defined herein, ismeant to include any salts of a peptide agent formed with a strong acid.The beneficial salts of peptide agents can be prepared by simple acidand base titration or neutralization. The beneficial salts of peptideagents can be prepared during its synthesis and purification processes.Alternatively, they can be prepared from peptide agent in the form of afree base. The free base is dissolved in a suitable liquid medium. Thissolution of the peptide agent is mixed with a solution of a strong acidto form the beneficial salts by removing the solvent through suitablemeans such as filtration or lyophilization. If the peptide agent is inits common commercially available form of a salt formed with a weak acid(i.e., pKa>3), the weak acid can be replaced by a strong acid throughcommon ion-exchange methods such as lyophilization, precipitation orother methods known in the art. For example, leuprolide acetate isdissolved in a suitable liquid medium, e.g., water. This solution of thepeptide agent is mixed with an aqueous solution of a strong acid such ashydrochloric acid. When the peptide acetate and a strong acid such ashydrochloric acid are dissolved in water, the peptide tends to beassociated with chloride ion, as the stronger acid HCl displaces theweaker carboxylic acetic acid. The solvent and liberated acetic acid (orother weak but volatile carboxylic acid) may be removed under vacuum.Thus, the mixture solution is freeze-dried to remove water and weakeracid to form the beneficial salts. If the peptide agent is not stableunder low pH, the beneficial salts of the peptide agent can be preparedthrough extensive dialysis against very low concentration of a strongacid.

The injectable polymeric compositions of the present invention maycontain peptide agent in a range of 0.01 to 40% by weight. In general,the optimal drug loading depends upon the period of release desired andthe potency of the peptide agent. Obviously, for peptide agent of lowpotency and longer period of release, higher levels of incorporation maybe required.

The term “biodegradable” refers to a material that gradually decomposes,dissolves, hydrolyzes and/or erodes in situ. Generally, the“biodegradable polymers” herein are polymers that are hydrolyzable,and/or bioerode in situ primarily through hydrolysis and/or enzymolysis.

The term “biodegradable polymer” as used herein is meant to include anybiocompatible and/or biodegradable synthetic and natural polymers thatcan be used in vivo, provided the polymer is at least substantiallyinsoluble in aqueous medium or body fluid. The term “substantiallyinsoluble” as used herein refers that the insolubility of the polymermust be sufficient to result in precipitation of the polymer in aqueousmedium or body fluid. Preferably, the solubility of the polymers is lessthan 1% by weight, and more preferably less than 0.1%. When the polymersolution in a water miscible or dispersible organic solvent is mixedwith an aqueous solution, the polymer will precipitate to form a solidor gelled matrix as the organic solvent dissipates. Suitablebiodegradable polymers are disclosed, e.g., in U.S. Pat. Nos. 4,938,763;5,278,201; 5,278,2012; 5,324,519; 5,702,716; 5,744,153; 5,990,194; and6,773,714. Some non-limiting examples of the polymers are polylactides,polyglycolides, polycaprolactones, polydioxanones, polycarbonates,polyhydroxybutyrates, polyalkylene oxalates, polyanhydrides,polyesteramides, polyurethanes, polyacetals, polyorthocarbonates,polyphosphazenes, polyhydroxyvalerates, polyalkylene succinates,poly(malic acid), and polyorthoesters, and copolymers, block copolymers,branched copolymers, terpolymers and combinations and mixtures thereof.

The block copolymers include A-B-A block copolymers, B-A-B blockcopolymers, and/or A-B block copolymers and/or branched copolymers. Thepreferred block copolymers are those wherein the A block comprises ahydrophobic polymer and the B block comprises a hydrophilic polymer.Particularly, when using one of the aforementioned block copolymers, themost preferred polymeric matrices are defined where the A block is abiodegradable polymer selected from the group consisting ofpolylactides, polyglycolides, poly(lactide-co-glycolide)s,polyanhydrides, poly(ortho ester)s, polyetheresters, polycaprolactones,polyesteramides, poly(ε-caprolactone)s, poly(hydroxybutyric acid)s, andblends and copolymers thereof, and the B block is polyethylene glycol ormonofunctionally derivatized polyethylene glycol such as methoxypolyethylene glycol. Many of these combinations may form acceptablethermal reversible gels.

Suitable molecular weights for polymers may be determined by a person ofordinary skill in the art. Factors that may be considered whendetermining molecular weights include desired polymer degradation rate,mechanical strength, and rate of dissolution of polymer in organicsolvents. Typically, a suitable range of weight averaged molecularweights of polymers is of about 2,000 Daltons to about 100,000 Daltonswith a polydispersity of from 1.1 to 2.5, depending upon which polymeris selected for use, among other factors.

The injectable polymeric compositions of the present invention maycontain biodegradable polymer in a range of 10% to 70% by weight. Theviscosity of the injectable compositions of the invention depends on themolecular weight of the polymer and organic solvent used. Typically,when the same solvent is used, the higher the molecular weight and theconcentration of the polymer, the higher the viscosity. Preferably theconcentration of the polymer in the compositions is less than 70% byweight. More preferably concentration of the polymer in the compositionsis between 30 to 60% by weight.

Poly(lactic acid), and copolymers of lactic acid and glycolic acid(PLGA), including poly(D, L-lactide-co-glycolide) andpoly(L-lactide-co-glycolide) are preferably used in the presentinvention. The polymers (or thermoplastic polyesters) have monomerratios of lactic acid to glycolic acid of between about 50:50 to about100:0 and weight average molecular weights of between about 2,000 toabout 100,000. The biodegradable thermoplastic polyesters can beprepared using the methods known in the art, e.g., polycondensation andring-opening polymerization (e.g., U.S. Pat. Nos. 4,443,340; 5,242,910;5,310,865, which are all incorporated herein by reference). The terminalgroups of the poly(DL-lactide-co-glycolide) can either be hydroxyl,carboxylic, or ester depending upon the method of polymerization. Thesuitable polymers may include a monofunctional alcohol or a polyolresidue and may not have a carboxylic acid terminus. Examples ofmonofunctional alcohols are methanol, ethanol, or 1-dodecanol. Thepolyol may be a diol, triol, tetraol, pentaol and hexaol includingethylene glycol, 1,6-hexanediol, polyethylene glycol, glycerol,saccharides, reduced saccharides such as sorbitol, and the like.

Many suitable PLGAs are available commercially, and the PLGAs ofspecific compositions can be readily prepared according to the priorart. The PLGAs of various monomer ratios and molecular weights areavailable from Boehringer-Ingelheim (Petersburg, Va., USA), LakeshoreBiomaterials (Birmingham, Ala., USA), DURECT Corporation (Pelham, Ala.).

The type, molecular weight, and amount of biodegradable polymer presentin the compositions can influence the length of time in which thepeptide agent is released from the controlled release implant. Theselection of the type, molecular weight, and amount of biodegradablepolymer present in the compositions to achieve desired properties of thecontrolled release implant can be determined by simple experimentations.

In one preferred embodiment of the present invention, the liquidcomposition can be used to formulate a controlled release deliverysystem for leuprolide hydrochloride. In such an embodiment, thebiodegradable thermoplastic polyester can preferably be 85/15 poly(DL-lactide-co-glycolide) containing a hydroxyl terminal group and alauryl ester terminus; can be present in about 30% to about 60% of thecomposition by weight; and can have an average molecular weight of about15,000 to about 50,000.

In another preferred embodiment of the present invention, the liquidcomposition can be used to formulate a controlled release deliverysystem for leuprolide hydrochloride. In such an embodiment, thebiodegradable thermoplastic polyester can preferably be 85/15 poly(DL-lactide-co-glycolide) containing two hydroxyl terminal groups; canbe present in about 30% to about 60% of the composition by weight; andcan have an average molecular weight of about 15,000 to about 50,000.

In still another preferred embodiment of the present invention, theliquid composition can be used to formulate a controlled releasedelivery system for leuprolide hydrochloride. In such an embodiment, thebiodegradable thermoplastic polyester can preferably be 85/15 poly(DL-lactide-co-glycolide) containing a carboxylic acid terminal groups;can be present in about 30% to about 60% of the composition by weight;and can have an average molecular weight of about 15,000 to about50,000.

In still another preferred embodiment of the present invention, thecomposition can be used to formulate a controlled release deliverysystem of leuprolide. In such an embodiment, the biodegradable polymercan preferably be 100/0 poly (DL-lactide) with/without carboxylic acidterminal groups; can be present in about 40% to about 60% of thecomposition by weight; and can have an average molecular weight of about8,000 to about 50,000.

The term “pharmaceutically acceptable organic solvent” is meant toinclude any biocompatible organic solvents that are miscible ordispersible in aqueous or body fluid. The term “dispersible” means thatthe solvent partially soluble or miscible in water. Preferably, a singlesolvent or a mixture of solvents has a solubility or miscibility inwater of greater than 0.1% by weight. More preferably, the solvent has asolubility or miscibility in water of greater than 3% by weight. Mostpreferably, the solvent has a solubility or miscibility in water ofgreater than 7% by weight. The suitable organic solvent should be ableto diffuse into body fluid so that the liquid composition coagulates orsolidifies. Single and/or mixture of such solvents can be employed; thesuitability of such solvents can be determined readily by simpleexperimentations.

Examples of pharmaceutically acceptable organic solvent include, but notlimited to, N-methyl-2-pyrrolidone, methoxypolyethylene glycol,alkoxypolyethylene glycol, polyethylene glycol esters, glycofurol,glycerol formal, methyl acetate, ethyl acetate, methyl ethyl ketone,dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, caprolactam,decylmethylsulfoxide, benzyl benzoate, ethyl benzoate, triacetin,diacetin, tributyrin, triethyl citrate, tributyl citrate, acetyltriethyl citrate, acetyl tributyl citrate, triethylglycerides, triethylphosphate, diethyl phthalate, diethyl tartrate, ethyl lactate, propylenecarbonate, ethylene carbonate, butyrolactone, and1-dodecylazacyclo-heptan-2-one, and combinations thereof.

The solubility of the biodegradable polymers in various pharmaceuticallyacceptable organic solvents will differ depending upon thecharacteristics of the polymers and their compatibility with varioussolvents. Thus, the same polymer will not be soluble to the same extentin different solvents. For example, PLGA has a much higher solubility inN-methyl-2-pyrrolidone (NMP) than that in triacetin. However, when PLGAsolution in NMP is in contact with aqueous solution, NMP will dissipatevery rapidly to form a solid polymer matrix due to its high watermiscibility. The fast diffusion rate of the solvent may result in asolid implant quickly, however, it may also lead to a high initial burstrelease. When PLGA solution in triacetin is in contact with aqueoussolution, triacetin will dissipate very slowly due to its low watermiscibility. The slow diffusion rate of the solvent may take a long timeto transform from a viscous liquid to a solid matrix. There may be anoptimum balance at which the solvent diffuse out and the coagulation ofthe polymer to encapsulate peptide agents. Therefore, it may beadvantageous to combine different solvents to obtain a desirabledelivery system. The solvents of low and high water miscibility may becombined to improve the solubility of the polymer, modify the viscosityof the composition, optimize the diffusion rate, and reduce the initialburst release,

The injectable polymeric compositions of the present invention typicallycontain an organic solvent in a range of 30% to 80% by weight. Theviscosity of the injectable compositions of the invention depends on themolecular weight of the polymer and organic solvent used. Preferably theconcentration of the polymer in the compositions is less than 70% byweight. More preferably concentration of the polymer in solutions isbetween 30 to 60% by weight.

The term “excipients” as used herein is meant to include any usefulingredient in the composition aside from the peptide agent or thebiodegradable polymers used to form the composition. Suitable excipientsinclude release rate modifying agents, burst effect reducing materials,buffering materials, antioxidants, and the like.

According to the present invention, suitable release rate modifyingagents include, but not limited to, amphiphilic compounds or copolymers,such alkanecarboxylic acid, oleic acid, alkyl alcohol, polar lipids,surfactants, copolymers of polyethyleneglycol and polylactide orpoly(lactide-co-glycolide), poloxamers, polyvinylpyrrolidone,polysorbates, and the like; esters of mono-, di-, and tricarboxylicacids, such as 2-ethoxyethyl acetate, triethyl citrate, acetyl tributylcitrate, acetyl triethyl citrate, glycerol triacetate, di(n-butyl)sebecate, and the like; polyhydroxy alcohols, such as polyethyleneglycol, sorbitol, and the like; fatty acids; triesters of glycerol, suchas triglycerides, medium-chain triglycerides such as MIGLYOL 810, 812,818, 829, 840, and the like. Mixtures of rate modifying agents can alsobe used in the polymer systems of the invention.

The release rate modifying agents may be present in the injectablepolymeric composition in an amount effective to reduce the initial burstof peptide agent released from the polymeric composition during thefirst 24 hours after implantation. Preferably, the polymeric compositionincludes about 1% to about 50% by weight, more preferably about 2% toabout 20% by weight of the release rate modifying agents.

According to the present invention, suitable buffering agents include,but are not limited to, inorganic and organic salts including calciumcarbonate, calcium hydroxide, calcium myristate; calcium oleate, calciumpalmitate, calcium stearate, calcium phosphate, magnesium carbonate,magnesium hydroxide, magnesium phosphate, magnesium myristate, magnesiumoleate, magnesium palmitate, magnesium stearate, zinc carbonate, zinchydroxide, zinc myristate, zinc oleate, zinc palmitate, zinc stearate,zinc phosphate, and combinations thereof.

The buffering agents may be present in the injectable polymericcomposition in an amount effective to stabilize the pH within theimplants during the degradation process. Preferably, the polymericcomposition includes about 1 wt % to about 30 wt %, more preferablyabout 2 wt % to about 15 wt % of the buffering agents.

According to the present invention, suitable antioxidants include, butare not limited to, d-alpha tocopherol acetate, ascorbyl palmitate,butylated hydroxyanidole, butylated hydroxyanisole,butylatedhydroxyquinone, hydroxycomarin, butylated hydroxytoluene, ethylgallate, propyl gallate, octyl gallate, lauryl gallate,propylhydroxybenzoate, trihydroxybutylrophenone, vitamin E, pegylatedvitamin E or vitamin E-TPGS, and the like.

The antioxidants may be present in the injectable polymeric compositionin an amount effective to scavenge any radicals or peroxides generatedwithin the implants. Preferably, the polymeric composition includesabout 1 wt % to about 30 wt %, more preferably about 3 wt % to about 15wt % of the antioxidants.

In one aspect the present invention provides a stabilized injectablebiodegradable polymeric composition for forming an economical,practical, and efficient controlled release delivery system for peptideagents comprises a) a beneficial salt of a peptide agent formed with astrong acid which minimizes or prevents the interaction/reaction betweenthe peptide agent and the polymer in an organic solution; b) abiodegradable polymer; c) a pharmaceutically acceptable organic solvent;and d) optionally one or more excipients to achieve optimal delivery ofthe peptide agent. Preferably, the injectable composition is packagedinto a kit comprising a step to fill the composition into a syringe in aready-to-use configuration. The composition in the kit is stable for areasonable period of time, preferably at least one year, to have asuitable storage shelf-life under controlled storage conditions. Thecomposition is preferably injected into a subject to form in situ animplant, from which the peptide agent is released in a therapeuticeffective amount over a desired, extended period of time.

The stabilized injectable biodegradable polymeric composition of thepresent invention can be prepared by appropriately combining abeneficial salt of a peptide agent, a biodegradable polymer, apharmaceutically acceptable organic solvent, and an optional excipient.The composition for administration may conveniently presented in dosageunit form and may be prepared by any of the methods known in the art ofpharmacy. One preferred method of preparing the composition of thepresent invention is to dissolve a biodegradable polymer and/or anexcipient in a pharmaceutically acceptable organic solvent to obtain auniform polymer solution/suspension first. Then the beneficial salt of apeptide agent is added to this solution/suspension. The components arethoroughly mixed using any proper means to obtain a uniform solution orsuspension. Then an appropriate amount of the solution or suspension istransferred into a syringe to obtain a ready-to-use product.

The level of incorporation of the beneficial salt and polymer in thecomposition of the invention will naturally vary, depending upon thepotency of the peptide agent component, the period of time over whichdelivery of the agent is desired, the solubility of the polymer in thesolvent, and the volume and viscosity of the injectable compositionwhich is desired to administer.

In certain preferred embodiments of the present invention, theinjectable biodegradable polymeric composition for forming aneconomical, practical, and efficient controlled release delivery systemfor peptide agents contains about 0.01% to 40% of the beneficial salt ofa peptide agent and about 10% to 70% of a poly(lactide-co-glycolide)polymer. The composition further contains about 30% to 70% of apharmaceutically acceptable organic solvent.

In a preferred embodiment of the present invention, the compositionfurther contains about 1% to 40% of a suitable excipient includingrelease rate modifying agents, burst effect reducing materials,buffering materials, antioxidants, tissue transporting agents and thelike as defined above.

According to the present invention, the injectable composition istransferred into a sterile container suitable for injectionadministration, e.g., a syringe. The container is packaged for storageand the components of the composition retains at least 80%, preferably90%, of their original molecular weight, structure and/or biologicalactivity during manufacturing and storage processes or prior toadministration to a subject such as an animal or human.

Thus, according to the present invention, the stabilized compositionscan be administered to a subject where controlled release delivery of apeptide agent is desired. As used herein, the term “subject” is intendedto include warm-blooded animals, preferably mammals, most preferablyhumans.

As used herein, the term “administered to a subject” is intended torefer to dispensing, delivering or applying a composition (e.g.,pharmaceutical formulation) to a subject by any suitable route fordelivery of the composition to the desired location in the subject.Preferably, the composition of the present invention can be administeredby injection and/or implantation subcutaneously, intramuscularly,intraperitoneally, or intradermally to provide the desired dosage basedon the known parameters for treatment of the various medical conditionswith the peptide agent.

The term “controlled release delivery”, as defined herein, is intendedto refer to continual delivery of a peptide agent in vivo over a periodof time following administration, preferably from at least several weeksto one year. Sustained controlled release delivery of the agent can bedemonstrated by, for example, the continued therapeutic effect of theagent over time (e.g., for an LHRH analogue, sustained delivery of theanalogue can be demonstrated by continued suppression of testosteronesynthesis over time). Alternatively, sustained delivery of the peptideagent may be demonstrated by detecting the presence of the agent in vivoover time.

The amount of the injectable composition administered will typicallydepend upon the desired properties of the controlled release implant.For example, the amount of the injectable composition can influence thelength of time in which the peptide agent is released from thecontrolled release implant.

In a preferred embodiment, the volume of the injectable polymericcomposition of the present invention to be injected to a subject rangesfrom 0.1 mL to 2.0 mL; preferably from 0.2 mL to 1.0 mL; and morepreferably from 0.3 mL to 0.5 mL.

The present invention further provides a method for in situ forming animplant in a subject comprising administering to a subject an effectiveamount of the injectable composition comprising: a) a beneficial salt ofa peptide agent formed with a strong acid which minimizes or preventsthe interaction/reaction between the peptide agent and the polymer in anorganic solution; b) a biodegradable polymer; c) a pharmaceuticallyacceptable organic solvent; and d) optionally one or more excipients toachieve optimal delivery of the peptide agent; and allowing the solventto dissipate into the surrounding aqueous environment to transform theliquid composition into a depot by phase separation. The depot may be aviscous gel, a semi-solid, or a solid matrix. The depot may also beporous or non-porous. The depot serves as the delivery system from whichthe peptide agent is released over a desired and extended period oftime.

In another preferred embodiment, the injectable composition of thepresent invention may be administered to fit into a body cavity to forma depot system. Such cavities include the cavities created after asurgery or natural body cavity such as vagina, anus, and the like.

In another aspect, the present invention provides a stabilized liquidbiodegradable polymeric composition for forming an economical,practical, and efficient controlled release delivery system for peptideagents comprises a) a beneficial salt of a peptide agent formed with astrong acid which minimizes or prevents the interaction/reaction betweenthe peptide agent and the polymer in an organic solution; b) abiodegradable polymer; c) an organic solvent; and d) optionally one ormore excipients to achieve optimal delivery of the peptide agent. Theliquid biodegradable polymeric composition may be fabricated intoimplantable polymeric matrices. Wherein the liquid biodegradablepolymeric composition retains at least 90%, preferably 95%, of theiroriginal molecular weight, structure and/or biological activity beforeand during the fabrication process.

As used herein, the term of “implantable polymeric matrices” is intendedto include particles, films, pellets, cylinders, discs, microcapsules,microspheres, nanospheres, microparticles, wafers, and other knownpolymeric configurations used for drug delivery.

Methods for forming various pharmaceutically acceptable polymer carriersare well known in the art. For examples, various methods and materialsare described in U.S. Pat. Nos. 6,410,044; 5,698,213; 6,312,679;5,410,016; 5,529,914; 5,501,863; and PCT Publication No. WO 93/16687;U.S. Pat. Nos. 4,938,763; 5,278,201; 5,278,202; EP 0,058,481; which areall incorporated herein by reference.

According to the present invention, the implantable polymeric matricesin the form of microspheres are produced by encapsulating the beneficialsalt of peptide agents into the polymer. The beneficial salt of peptideagents can be encapsulated using various biocompatible and/orbiodegradable polymers having unique properties that are suitable fordelivery to different biological environments or for effecting specificfunctions. The rate of dissolution and, therefore, delivery of peptideagent is determined by the particular encapsulation technique, polymercomposition, polymer crosslinking, polymer thickness, polymersolubility, size and solubility of biologically activecompound/polyanion complex.

The beneficial salts of peptide agents to be encapsulated are dissolvedor suspended in a polymer solution in an organic solvent. The polymersolution must be concentrated enough to completely coat the beneficialsalt after they are added to the solution. Such an amount is one thatprovides a weight ratio of the beneficial salt of peptide agents topolymer between about 0.01 and about 50, preferably between about 0.1and about 30. The beneficial salt of peptide agents should be keptsuspended and not allowed to aggregate as they are coated by contactwith the polymer.

A polymer solution of the beneficial salts of peptide agents cantherefore be subjected to a variety of microencapsulation techniquesincluding spray drying, spray congealing, emulsion, and solventevaporation emulsion.

According to one embodiment of the invention, the beneficial salt ofpeptide agents is dissolved or suspended in a polymer solution in anorganic solvent. The solution or suspension is transferred to a largervolume of an aqueous solution containing an emulsifier. In the aqueoussolution, the organic phase is emulsified, where the organic solventevaporates or diffuses away from the polymer. The solidified polymerencapsulates the beneficial salt of peptide agents to form a polymermatrix. The emulsifier helps to reduce the interfacial surface tensionbetween the various phases of matter in the system during the hardeningphase of the process. Alternatively, if the encapsulating polymer hassome inherent surface activity, there may be no need for addition of aseparate surface-active agent.

Emulsifiers useful to prepare encapsulated the beneficial salt ofpeptide agents according to the present invention include poloxamers andpolyvinyl alcohol as exemplified herein, surfactants and other surfaceactive compounds which can reduce the surface tension between thepolymer encapsulated beneficial salt of peptide agents and the solution.

Organic solvents useful to prepare the microspheres of the presentinvention, except for those disclosed above, also include acetic acid,acetone, methylene chloride, ethyl acetate, chloroform and othernon-toxic solvents that will depend on the properties of the polymer.Solvents should be chosen to dissolve the polymer and are ultimatelynon-toxic.

Thus, according to the present invention, these implantable polymericmatrices can be administered to a subject where sustained controlledrelease delivery of a peptide agent is desired. Preferably, theimplantable polymeric matrices of the invention can be administered byinjection and/or implantation subcutaneously, intramuscularly,intraperitoneally, or intradermally to provide the desired dosage basedon the known parameters for treatment of the various medical conditionswith the peptide agent.

All books, articles and patents referenced herein are fully incorporatedby reference.

EXAMPLES

The following examples illustrate the compositions and methods of thepresent invention. The following examples should not be considered aslimitations, but should merely teach how to make the useful controlledrelease drug delivery compositions.

Example 1. Preparation of Beneficial Salts of Peptide Agents and PeptideDerivatives Formed with Strong Acids

Peptide agent or peptide derivative containing at least one basicfunctional group is dissolved in water. Stoichiometric amounts of astrong acid are added to the aqueous solution of the peptide agent,resulting in neutralization of the basic groups in the peptide agent.The salt is obtained by precipitation, filtration and/or lyophilization.

Example 2. Preparation of Leuprolide Hydrochloride

Leuprolide is a luteinizing hormone releasing hormone (LHRH) agonistcontaining 9 amino acid residues and two basic functionalities (ahistidine and an arginine group). Its N-terminal amine was blocked inthe form of pyroglutamic acid. It has been used in the treatment ofprostate cancer and endometriosis. Leuprolide acetate (LA-Ac) wasobtained from Polypeptides Laboratories, Inc. (PPL Lot#PPL-LEUP0401A).Leuprolide Hydrochloride (LA-HCl) was prepared by replacing acetic acidwith HCl through an ion-exchange and lyophilization process. Typically,1000 mg of leuprolide acetate was dissolved in 30 mL water. 3.19 mL of0.5 N HCl (HCl:LA˜2.2:1) was added and mixed well. The solution wasfreeze-dried for 72 h to remove acetic acid. The dried powder wasre-dissolved in water and freeze-dried again.

Example 3. Preparation of Leuprolide Mesylate

343.5 mg of leuprolide acetate (PPL Lot#PPL-LEUP0401A) was dissolved in20 mL water. 324 μL of methanesulfonic acid was added and mixed well(molar ratio of leuprolide acetate to methanesulfonic acid ˜1:2). Thesolution was freeze-dried for 72 h to remove acetic acid. The driedpowder was re-dissolved in water and freeze-dried again.

Example 4. Preparation of Goserelin Hydrochloride

766 mg of goserelin acetate (PPL Lot#0603-219) was dissolved in 20 mLwater. 2.12 mL of 0.5 N HCl (molar ration of HCl:goserelinacetate˜2.2:1) was added and mixed well. The solution was freeze-driedfor 72 h to remove acetic acid. The dried powder was re-dissolved inwater and freeze-dried again.

Example 5. Preparation of Palmitoyl-Octreotide (PAL-OCT)

50 mg of octreotide acetate was dissolved in 1000 uL of anhydrous DMSOcontaining 100 uL TEA. 17.1 mg of Palmitic acid N-hydroxysuccinimideester (Mw 353.50) was dissolved in 3 mL anhydrous DMSO and added bydirect injection to the peptide solution. The reaction was allowed toproceed for overnight at room temperature. The mixture was poured intodiethyl ether to precipitate palmitoylated octreotide. The precipitatewas washed with diethyl ether twice and then dried under vacuum. Theresulting acylated peptide was in a form of white powder. The beneficialsalt of the acylated peptide was formed by neutralizing the residualbasic amine groups using a strong acid.

Example 6. Preparation of Decanal-Octreotide (DCL-OCT)

50 mg of octreotide was dissolved in 2 mL of 20 mM sodiumcyanoborohydride (Mw 62.84, NaCNBH₃) (2.51 mg) solution in 0.1 M acetatebuffer at pH 5. 13.7 mg of Decanal (Mw 156.27) (OCT:DCL=1:2) was addedby direct injection to the peptide solution. The reaction was allowed toproceed for overnight at 4° C. The mixture was separated bycentrifugation. The precipitated PAL-OCT was freeze-dried. Thebeneficial salt of the acylated peptide was formed by neutralizing theresidual basic amine groups using a strong acid.

Example 7. Preparation of PEGylated Octreotide

A solution of octreotide acetate (10 mg/mL) in water was added to a vialcontaining 2 molar equivalent amount of succinimidyl propionatemonomethoxy PEG (SPA-m PEG, MW 2000 dalton) in 0.1 M phosphate buffer atpH 7.4. The reaction was allowed to proceed with stirring at 4° C.overnight. Then the reaction mixture was separated by usingreversed-phase HPLC (RP-HPLC) on C-18 (YMC ODS-A 4.6×250 mm, 5 um,Waters Corporation). The mobile phase consisted of 0.1% TFA in water (A)and CAN containing 0.1% TFA (B). The mobile phase was run with a lineargradient from 30 to 60% eluent B for 20 min at a flow rate of 1 ml/minand the UV absorbance of the elution was monitored at 215 nm. Theelution fractions corresponding to respective peaks were collectedseparately, purged with nitrogen, and lyophilized.

Alternatively, site-specific PEGylation of octreotide can be obtained. Asolution of octreotide acetate (10 mg/mL) in 20 mM sodiumcyanoborohydride (NaCNBH₃) and 0.1 M acetate buffer at pH 5 was added toa vial containing 3 molar equivalent amount of monomethoxyPEG-propionaldehyde (ALD-mPEG, MW 2000 dalton) in water. The reactionwas allowed to proceed with stirring at 4° C. overnight. Then thereaction mixture was separated by using reversed-phase HPLC (RP-HPLC) onC-18 (YMC ODS-A 5 μm, 4.6×250 mm, Waters Corporation). The mobile phaseconsisted of 0.1% TFA in water (A) and CAN containing 0.1% TFA (B). Themobile phase was run with a linear gradient from 30 to 60% eluent B for20 min at a flow rate of 1 ml/min and the UV absorbance of the elutionwas monitored at 215 nm. The elution fractions corresponding torespective peaks were collected separately, purged with nitrogen, andlyophilized. The beneficial salt of the pegylated peptide is formed byneutralizing the residual basic amine groups using a strong acid.

Example 8. Stability of Peptide Agent and Biodegradable Polymer inInjectable Polymeric Compositions

Poly(DL-lactide-co-glycolide) (PLGA) of an 85/15 ratio of lactide toglycolide (DLPLG85/15, IV: 0.28) with a lauryl ester end group wasdissolved in N-methyl-2-pyrrolidone (NMP) to give a 50% solution byweight. The leuprolide salts were mixed with the PLGA solution in NMP togive a uniform injectable composition at ratios shown in the Table 1.The injectable compositions were filled into 1.2 mIL polypropylenesyringes with luer-lock tips. Then the pre-filled syringes were sealedusing luer-lock caps. The capped syringes were packaged in a containerand sealed in a plastic bag under vacuum and then stored at 4° C. androom temperature (˜22° C.) for up to 18 months. The injectablecomposition was sampled at 24 h, 1, 2, 3, 6, 12, and 18 month timepoints. Purity of leuprolide in the sample was determined by HPLC.Molecular weight of the polymer was determined by gel permeationchromatography (GPC) using polystyrene standards with known molecularweights.

TABLE 1 Injectable polymeric formulations tested Leuprolide Salt DLPLG8515/NMP Drug load Samples (mg) (mg) (%, w/w) Blank 0 1000 0 LA-Ac 50890 5.3 LA-MS 54 960 5.3 LA-HCI-1 106 940 10.1 LA-NCI-2 41 730 5.3

It was surprisingly found that the use of hydrochloride and mesylatesalts of leuprolide instead of acetate significantly reduced thedegradation of leuprolide and polymer in PLGA solutions in NMP at both4° C. and room temperature over time. Tables 2 and 3 showed thedegradation of leuprolide in PLGA solutions in NMP at 4° C. and roomtemperature over time respectively. At 4° C., up to 23% of leuprolidewas degraded in the polymeric composition containing leuprolide acetate,while less than 2% of leuprolide was degraded for those formulationscontaining leuprolide hydrochloride and leuprolide mesylate after 18months. At room temperature, more than 35% degradation of leuprolide wasobserved for leuprolide acetate formulations, while only about 11% forleuprolide hydrochloride and leuprolide mesylate formulations after 12months. In addition, at room temperature, the color change (from milkyto yellow to rusty color) and phase separation were observed. The phaseseparation resulted in heterogeneous formulations and uneven degradationof the peptide and the polymer in the formulation. The heterogeneity ofthe formulations may be the cause for the fluctuation of the resultsobtained at various time points.

TABLE 2 Stability of Leuprolide in PLGA/NMP Formulation at 4° C. Time(M) LA-AC LA-HCI-1 LA-MS 0 100.0 100.0 100.0 1 89.3 100.0 100.0 3 100.0100.0 100.0 6 94.1 100.0 100.0 12 88.2 100.0 98.9 18 76.9 98.5 98.3

TABLE 3 Stability of Leuprolide in PLGA/NMP Formulation at RT Time (M)LA-AC LA-HCI-1 LA-NCI-2 LA-MS 0 100 100 100 100 1 75 99 100 95 2 78 9897 97 3 86 100 100 100 6 87 99 100 99 12 65 89 89 89

Table 4 and 5 showed the changes of molecular weight of the polymer indifferent formulations. Comparing to blank control, the molecular weightof PLGA in leuprolide acetate formulation decreased more than 10% at 4°C. and more than 90% at room temperature after 6 months. The molecularweight of PLGA in leuprolide hydrochloride and leuprolide mesylateformulations was the same as that of the blank control at both 4° C. andRT even after 12 months. However, after 12 months, more than 90% of thepolymer from both blank control and leuprolide hydrochloride andleuprolide mesylate formulations was degraded. The results indicate thatthe salts of leuprolide formed with strong acid such as HCl andmethanesulfonic acid completely prevent the interaction/reaction betweenthe peptide and PLGA in solution. While the weak acid such as aceticacid does not prevent the deleterious interaction/reaction between thepeptide and PLGA in solution. Thus, the improvement of the stability ofthe formulation by using the salt of the peptide formed with a strongacid enables the manufacturing of a ready-to-use injectable compositionwith a satisfactory storage stability of at least one year.

TABLE 4 Molecular Weight of PLGA in Different Formulations over time at4° C. Time (M) Blank LA-AC LA-HCI-1 LA-MS 0 24655 23842 24369 24556 125214 24282 25203 24574 3 24567 22775 24833 24833 6 23935 21957 2466124034 12 23905 18906 23837 23393 18 22178 16107 22802 22227

TABLE 5 Molecular Weight of PLGA in Different Formulations over time atroom temperature Time (M) Blank LA-AC LA-HCI-1 LA-HCI-2 LA-MS 0 24655.024282 24567 24468 24468 1 24282.2 20526 25022 25022 24832 2 22969.315459 23230 23230 22969 3 23227.7 11073 23228 23311 21872 6 ND 340918998 17952 15114 12 3112.3 380 4236 3388 2531

Example 9. Stability of Leuprolide and Polymer in Injectable PolymericCompositions

Poly(DL-lactide-co-glycolide) (PLGA) of an 85/15 ratio of lactide toglycolide (DLPLG85/15, IV: 0.28) with a lauryl ester end group wasdissolved in dimethylsulfoxide (DMSO) to give a 50% solution by weight.The leuprolide salts were mixed with the PLGA solution in DMSO to give auniform injectable composition at ratios shown in the Table 6. Theinjectable compositions were filled into 1.2 mIL polypropylene syringeswith luer-lock tips. Then the pre-filled syringes were sealed usingluer-lock caps. The capped syringes were packaged in a container andsealed in a plastic bag under vacuum and then stored at 4° C. and roomtemperature (˜22° C.) for up to 16 months. The injectable compositionwas sampled at pre-defined time points. Purity of leuprolide in thesample was determined by HPLC. Molecular weight of the polymer wasdetermined by gel permeation chromatography (GPC) using polystyrenestandards with known molecular weights.

TABLE 6 Injectable polymeric compositions tested Leuprolide Salt DLPLG8515 in Drug load Samples (mg) DMSO (mg) (%, w/w) Blank 0 4000 0 LAAc200.4 4788 4 LAMS-3 200.0 4806 4 LAHCI-3 202.8 4810 4

It was surprisingly found that the use of hydrochloride and mesylatesalts of leuprolide instead of acetate significantly reduced thedegradation of leuprolide and polymer in PLGA solutions in DMSO at 4° C.over time. FIGS. 1 and 2 showed the degradation of leuprolide in PLGA insolutions in DMSO at 4° C. over time. Up to about 20% of leuprolide wasdegraded in the case of leuprolide acetate, while less than 5% ofleuprolide was degraded for leuprolide hydrochloride and leuprolidemesylate formulations after 16 months. FIG. 5 showed the changes ofmolecular weight of PLGA in different formulations. Comparing to blankcontrol, the molecular weight of PLGA in leuprolide acetate formulationdecreased about 40% at 4° C. after 16 months. The molecular weight ofPLGA in injectable polymeric compositions containing leuprolidehydrochloride and leuprolide mesylate was comparable to that of thecontrol at 4° C. after 16 months. The results indicate that the salts ofleuprolide formed with strong acid such as HCl and methanesulfonic acidalmost completely prevent the interaction/reaction between the peptideand PLGA in DMSO solution. While the weak acid such as acetic acid doesnot prevent the deleterious interaction/reaction between the peptide andPLGA in DMSO solution.

Example 10. In Vitro Release of Leuprolide from Injectable PolymericFormulations

Three polymer vehicle solutions were prepared as following: PLG 85/15(0.28 IV) with a lauryl ester end group was dissolved in NMP at 50% and55% by weight, and RG503 (0.42 IV) with a carboxylic acid end group wasdissolved in NMP at 50% by weight. Then suitable amount of leuprolidehydrochloride (LAHCl) and leuprolide mesylate (LAMS) were mixed with thepolymer solutions at 6% by weight each. The formulations were thoroughlymixed to obtain uniform formulations.

An aliquot of the formulation suspension (about 100 mg) was injectedinto in 3 mL phosphate buffer saline solution at pH 7.4 with 0.1% sodiumazide at 37° C. The receiving fluid was replaced at selected time pointswith fresh buffer solution, and the removed buffer solution diluted2-fold with phosphate buffer at pH 7.4 was analyzed for drugconcentration by HPLC. The amount released at each time point wascalculated. FIG. 3 shows the cumulative release of leuprolide fordifferent formulations over time.

As shown in FIG. 3, there is no significant difference in leuproliderelease between LAHCl and LAMS. However, the type and the concentrationof PLGA seem to affect the release of leuprolide significantly. Therelease rate of leuprolide from RG503H formulation was much faster thanthat from PLG85/15 formulations. Thus, RG503H may be suitable forshorter-term delivery of leuprolide, while PLG85/15 may be useful forlonger-term delivery of the peptide. The release rate of the peptide canalso be further modified by changing the concentration of the PLGA. Asthe concentration of PLG85/15 was increased from 50% to 55%, the initialrelease rate of leuprolide was significantly reduced. Thus, theparameters for a specific formulation for the peptide to achieve adesired release profile can be readily obtained by simpleexperimentations.

Example 11. Effect of Excipients on the In Vitro Release of Leuprolide

The polymer vehicle solutions with and without excipients were preparedas following: PLA 100DLPL (0.26 IV, Lakeshore, Ala.) with a lauryl esterend group and Vitamin E TPGS were dissolved in NMP at suitable amountaccording to the Table 7. Then suitable amount of leuprolidehydrochloride (LAHCl) was mixed with the polymer solutions at 15% byweight. The formulations were thoroughly mixed to obtain uniformformulations.

TABLE 7 Effect of excipients on the in vitro release of leuprolide PLA100DLPL NMP Vitamin E LAHCl Sample (%) (%) TPGS (%) (%) Formulation-1 4738 0 15 Formulation-2 44.5 36.4 4.2 15

An aliquot of the formulation suspension (about 100 mg) was injectedinto in 3 mL phosphate buffer saline solution at pH 7.4 with 0.1% sodiumazide at 37° C. The receiving fluid was replaced at selected time pointswith fresh buffer solution, and the removed buffer solution diluted10-fold with PBS at pH 7.4 was analyzed for drug concentration by HPLC.The amount released at each time point was calculated. FIG. 4 shows thecumulative release of leuprolide for different formulations over time.

As shown in FIG. 4, the incorporation of Vitamin E TPGS did not affectthe initial burst, but seemed to reduce the release rate of leuprolideat later stages. Thus, Vitamin E TPGS may be useful for extending thedelivery of the peptide and also functioning as an antioxidant.

Example 12. Effect of Excipients on the In Vitro Release of Leuprolide

The polymer vehicle solutions with and without excipients were preparedas following: PLA 100D040 (0.34 IV, Durect, Calif.) with a lauryl esterend group and medium chain triglyceride Miglyol 812 were dissolved inNMP at suitable amount according to the Table 8. Then suitable amount ofleuprolide hydrochloride (LAHCl) was mixed with the polymer solutions at15% by weight. The formulations were thoroughly mixed to obtain uniformformulations.

TABLE 8 Effect of excipients on the in vitro release of leuprolide PLA100D040 NMP Miglyol 812 LAHCl Sample (%) (%) (%) (%) Formulation-1 42.542.5 0 15 Formulation-2 42.5 38.3 4.2 15

An aliquot of the formulation suspension (about 100 mg) was injectedinto a vial containing 3 mL phosphate buffer saline solution at pH 7.4with 0.1% sodium azide at 37° C. The receiving fluid was replaced atselected time points with fresh buffer solution, and the removed buffersolution diluted 10-fold with PBS at pH 7.4 was analyzed for drugconcentration by HPLC. The amount released at each time point was backcalculated using a standard curve. FIG. 5 shows the cumulative releaseof leuprolide for different formulations over time.

As shown in FIG. 5, the incorporation of Miglyol 812 did significantlyreduced the initial burst release of leuprolide, and seem to maintainthe release rate of leuprolide at later stages. Thus, Miglyol 812 may beuseful for extending the delivery of the peptide. Comparing to theresults in Example 11, it seems the molecular weight of the polymer alsosignificantly affect the initial burst release of leuprolide. It seemsthat the smaller molecular weight of the PLA, the smaller the initialburst release rate of leuprolide.

Example 13. In Vivo Release of Leuprolide

Poly(DL-lactide-co-glycolide) of an 85/15 ratio of lactide to glycolide(DLPLG85/15, IV: 0.28) containing a lauryl ester end group was dissolvedin N-methyl-2-pyrrolidone (NMP) to give a 55% solution by weight. Theleuprolide salt, i.e., Leuprolide mesylate or Leuprolide HCl, were mixedwith the PLGA solution in NMP to give a uniform injectable formulationat a drug loading of about 12%. The injectable formulations weretransferred into 1.2 ml polypropylene syringes with luer-lock tips and a19 gauge thin-wall needle attached. Each formulation was then injectedinto the rats subcutaneously at a volume of about 100 μL with 6 animalsper group. The serum samples were collected from each animal at 3 hour,1, 3, 7, 14, 28, 42, 56, and 70 days post injection. The serum sampleswere analyzed for leuprolide concentration by ELISA using the kitsavailable from Peninsula Laboratories Inc. The leuprolide remaining inthe implants at various times was analyzed by HPLC.

FIG. 6 shows the release profile of leuprolide from two differentformulations up to 70 days. Both formulations showed initial burstrelease of leuprolide. The formulation containing LAHCl reached C_(max)of 661.6 ng/mL at 3 hours, and the formulation containing LAMS reachedC_(max) of 370.6 ng/mL also at 3 hours. Both formulations showedsustained release of leuprolide over an extended time period. Theformulation containing LAMS showed a more constant serum levels ofleuprolide than that obtained from the formulation containing LAHCl.

Example 14. In Vivo Release of Leuprolide

Poly(DL-lactide-co-glycolide) of a 85/15 ratio of lactide to glycolide(DLPLG85/15, IV: 0.27) containing a 1,6-hexanediol moiety is dissolvedin N-methyl-2-pyrrolidone (NMP) to give a 50% solution by weight. Theleuprolide salt, i.e., Leuprolide acetate or Leuprolide HCl, are mixedwith the PLGA solution in NMP to give a uniform injectable formulationat a drug loading of about 12%. The injectable formulations aretransferred into 1.2 ml polypropylene syringes with luer-lock tips and a19 gauge thin-wall needle attached. Each formulation is then injectedinto the rats subcutaneously at a volume of about 100 μL with 6 animalsper group. The serum samples are collected from each animal at 3 hour,1, 3, 7, 14, 28, 42, 56, 70, 91, 112, 133, 154, 175, and 206 days postinjection. The serum samples are analyzed for leuprolide concentrationby ELISA using the kits available from Peninsula Laboratories Inc., andfor testosterone concentration by LC/MS/MS. The leuprolide remaining inthe implants at various times may be analyzed by HPLC.

Similar experiments can be designed and performed using other LHRHanalogues such as buserelin, deslorelin, fertirelin, histrelin,lutrelin, goserelin, nafarelin, triptorelin, cetrorelix, abarelix, andother peptides, such as GLP-1, PYY, etc, and other polymers andsolvents.

Example 15. Use of the Stabilized Injectable Polymeric Compositions

The administration of the stabilized injectable polymeric composition toa patient may be accomplished in a number of ways. A biodegradablepolymeric composition may be injected subcutaneously or intramuscularlyto form an implant in situ, applied as a transdermal cream, and alsointroduced to the patient as a rectal or vaginal suppository.

Example 16. Preparation of Polymer Microspheres Containing LAHCl

Poly(lactide-co-glycolide (PLGA) microspheres are prepared by anoil-in-water (O/W) single emulsion technique. PLGA is dissolved inmethylene chloride (DCM). For the encapsulation of LAHCl, the drug ismixed with the PLGA solution in DCM. The mixed solution or suspension isemulsified in 500 mL of 0.5-1% (w/v) PVA (PVA, 88% hydrolyzed, averagemolecular weight of 31,000-50,000, Sigma-Aldrich) solution pre-cooled inthe refrigerator at 4° C. The emulsion is stirred continuously for 3 hat RT to evaporate the DCM. The hardened microspheres are collected,washed three times with deionized water, and then freeze-dried.

Example 17. Use of the Stabilized Liquid Polymeric Composition forPreparing Implantable Polymer Matrices

The biodegradable polymer consisting of a poly-(lactic acid-co-glycolicacid) having a ratio of lactide to glycolide of 50:50 to 100:0 such asRG503H (Boehringer Ingelheim Chemicals, Inc. USA) is dissolved in avolatile organic solvent, such as ethyl acetate or methylene chloride.An appropriate amount of a beneficial salt as defined herein such asgoserelin mesylate (0.01%-30% by weight relative to the polymer) isdissolved/dispersed in the polymer solution. The solution is thoroughlymixed to obtain a uniform solution or suspension. After the mixing iscomplete, the solvent is removed by evaporation. This is done by a spraydrying procedure to form small uniform particles for injection. This canbe done also in a mold to form an implant. The resulting polymermatrices can also be ground to a powder and formulated as an injectablesuspension.

Thus obtained solid dosage forms can be injected subcutaneously orintramuscularly, or can be placed surgically under the skin in the formof an implant, or given orally as part of an oral delivery system forpeptide agents. The solid microparticles may also be prepared as asuspension or a non-aqueous solution, which may also be administered toa patient via inhalation, for pulmonary drug delivery. Themicroparticles may also be suspended in oil and introduced to thepatient as a rectal or vaginal suppository.

What is claimed is:
 1. A method of forming an injectable polymericcomposition comprising the steps of, (a) dissolving a biodegradablepolymer selected from the group of polylactide, poly(lactic acid),poly(lactic acid-co-glycolic acid) and poly(lactide-co-glycolide) in apharmaceutically acceptable organic solvent to form a polymer solutionand, (b) mixing the polymer solution with a salt of a luteinizinghormone releasing hormone (LHRH) analogue formed with a strong acidselected from the group consisting of methanesulfonic acid, hydrochloricacid, and sulphuric acid.
 2. The method of forming the injectablepolymeric composition in claim 1, wherein the pharmaceuticallyacceptable organic solvent is selected from the group consisting ofN-methyl-2-pyrrolidone (NMP) and Dimethyl sulfoxide (DMSO).
 3. Themethod of forming the injectable polymeric composition in claim 1,wherein the LHRH analogue is an LHRH agonist selected from the groupconsisting of leuprorelin, buserelin, gonadorelin, deslorelin,fertirelin, histrelin, lutrelin, goserelin, nafarelin, triptorelin,enfuvirtide, and thymosin α1.
 4. The method of forming the injectablepolymeric composition in claim 1, wherein the LHRH analogue is an LHRHantagonist selected from the group consisting of cetrorelix andabarelix.
 5. The method of forming the injectable polymeric compositionin claim 1, wherein the biodegradable polymer has an average molecularweight of between 2,000 and 100,000 Dalton.
 6. The method of forming theinjectable polymeric composition in claim 1, wherein the biodegradablepolymer is manufactured with a dodecanol (or lauryl alcohol) as aninitiator resulting in the polymer with one hydroxyl end group at oneend and one dodecyl ester group at the other end.
 7. The method offorming the injectable polymeric composition in claim 1, wherein thebiodegradable polymer is manufactured with a 1,6-hexanediol as aninitiator resulting in the polymer with one hydroxyl group at both endsof the polymer.
 8. A method of forming an injectable polymericcomposition comprising the steps of, (a) dissolving a biodegradablepolymer selected from the group of polylactide, poly(lactic acid),poly(lactic acid-co-glycolic acid) and poly(lactide-co-glycolide) inN-methyl-2-pyrrolidone to form a polymer solution and, (b) mixing thepolymer solution with a salt of a luteinizing hormone releasing hormone(LHRH) analogue formed with a strong acid selected from the groupconsisting of methanesulfonic acid, hydrochloric acid, and sulphuricacid, wherein percentage of the biodegradable polymer in the injectablepolymeric composition is 40-60% w/w, percentage of the salt of theluteinizing hormone releasing hormone in the injectable polymericcomposition is 0.01-40% w/w, and percentage of N-methyl-2-pyrrolidone inthe injectable polymeric composition is 30-80% w/w, wherein theinjectable polymeric composition does not contain excess of the strongacid.
 9. The method of forming an injectable polymeric composition inclaim 8, wherein the biodegradable polymer has an average molecularweight between 8,000 and 50,000 Dalton.
 10. A method of forming aninjectable polymeric composition comprising the steps of, (a) dissolvinga biodegradable polymer selected from the group consisting ofpoly(lactic acid-co-glycolic acid) and poly(lactide-co-glycolide),having the ratio of lactide:glycolide or lactic acid:glycolic acid offrom 50:50 to 100:0, in N-methyl-2-pyrrolidone to form a polymersolution and, (b) mixing the polymer solution with a salt of aluteinizing hormone releasing hormone analogue formed with a strong acidselected from the group consisting of methanesulfonic acid, hydrochloricacid, and sulphuric acid, wherein percentage of the biodegradablepolymer in the injectable polymeric composition is 30-60% w/w,percentage of the salt of the luteinizing hormone releasing hormone inthe injectable polymeric composition is 0.01-40% w/w, and percentage ofN-methyl-2-pyrrolidone in the injectable polymeric composition is 30-80%w/w, wherein the injectable polymeric composition does not containexcess of the strong acid.
 11. The method of forming an injectablepolymeric composition in claim 10, wherein the poly(lactide-coglycolide)or poly(lactic acid-co-glycolic acid) has a ratio of lactide:glycolideor lactic acid:glycolic acid of 85:15.
 12. The method of forming aninjectable polymeric composition in claim 10, wherein thepoly(lactide-coglycolide) or poly(lactic acid-co-glycolic acid) has anaverage molecular weight between 15,000 and 50,000 Dalton.